Sean Pywell wrote:
> and that this is called manna. Gliders are well known for feeding on
> exudates from trees - is this just standard sap that they obtain by
> cutting into the phloem? or is it something else that the tree
> produces to plug the wound? And if so, is the same response given to
> insect attack, and does this consitute manna? And do birds feed on
> any such exudate, or do they stick just to lerps?
Yellow-bellied Gliders (Petaurus australis) - a gliding possum - are well
known for their habit of deeply incising various Eucalyptus species to feed
on phloem sap. Other Petaurus gliders feed on tree exudates which they
gain from incising the bark - Sugar Gliders famously with wattles (Acacia)
and Mahogany Gliders less famously with grasstree flower spikes
In 'Emu' Volume 99: 69-72, a paper documents a novel foraging guild for
Australia - sap-suckers - birds feeding at Yellow-bellied Glider sap-sites
on Red Mahogany (Eucalyptus resinifera) in North Queensland. The main
users of this phloem sap there are Rainbow Lorikeet, Scaly-breasted
Lorikeet, Crimson Rosella, White-naped Honeyeater and White-cheeked
Honeyeater. Occasional users include other honeyeaters, Pied Currawong,
Victoria's Riflebird, etc.
In the Otway Ranges of southwestern Victoria, Yellow-bellied Gliders are
also found, and in some Blue Gum (E. globulus) forests are quite abundant.
In one such forest near Lorne, I have observed birds and insects feeding on
phloem sap at the glider sites. The birds were Red Wattlebird, Little
Wattlebird, New Holland Honeyeater, White-eared Honeyeater and Crescent
Honeyeater. Red Wattlebirds dominate the most productive sites - much as
they do major nectar sources. Insects included the butterflies -
Australian Admiral (Vanessa itea) and Australian Painted Lady (V.
kershawi). This foraging opportunity is possibly quite a significant one -
maybe a major carbohydrate source for birds outside the main flowering
times of forest trees???
As far as the terminology goes for these tree exudates, I'm not quite up to
speed. My recollection is that Eucalyptus species exude the reddish 'kino'
into more serious wounds to "plug them up". Kino is rarely seen at
Yellow-bellied Glider sap-sites, suggesting that their incisions to tap
phloem sap are not deep enough to elicit a major response from the tree.
In some areas I have seen such extensive scarring on a tree from glider
feeding that the tree seemed doomed, but I've not yet seen a tree die from
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